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/* reducer_string.h -*- C++ -*-
*
* Copyright (C) 2009-2016, Intel Corporation
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Intel Corporation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* *********************************************************************
*
* PLEASE NOTE: This file is a downstream copy of a file mainitained in
* a repository at cilkplus.org. Changes made to this file that are not
* submitted through the contribution process detailed at
* http://www.cilkplus.org/submit-cilk-contribution will be lost the next
* time that a new version is released. Changes only submitted to the
* GNU compiler collection or posted to the git repository at
* https://bitbucket.org/intelcilkruntime/intel-cilk-runtime.git are
* not tracked.
*
* We welcome your contributions to this open source project. Thank you
* for your assistance in helping us improve Cilk Plus.
*/
/** @file reducer_string.h
*
* @brief Defines classes for doing parallel string creation by appending.
*
* @ingroup ReducersString
*
* @see ReducersString
*/
#ifndef REDUCER_STRING_H_INCLUDED
#define REDUCER_STRING_H_INCLUDED
#include <cilk/reducer.h>
#include <string>
#include <list>
/** @defgroup ReducersString String Reducers
*
* String reducers allow the creation of a string by concatenating a set of
* strings or characters in parallel.
*
* @ingroup Reducers
*
* You should be familiar with @ref pagereducers "Intel(R) Cilk(TM) Plus reducers",
* described in file reducers.md, and particularly with @ref reducers_using,
* before trying to use the information in this file.
*
* @section redstring_usage Usage Example
*
* vector<Data> data;
* void expensive_string_computation(const Data& x, string& s);
* cilk::reducer<cilk::op_string> r;
* cilk_for (int i = 0; i != data.size(); ++i) {
* string temp;
* expensive_string_computation(data[i], temp);
* *r += temp;
* }
* string result;
* r.move_out(result);
*
* @section redstring_monoid The Monoid
*
* @subsection redstring_monoid_values Value Set
*
* The value set of a string reducer is the set of values of the class
* `std::basic_string<Char, Traits, Alloc>`, which we refer to as "the
* reducer's string type".
*
* @subsection redstring_monoid_operator Operator
*
* The operator of a string reducer is the string concatenation operator,
* defined by the "`+`" binary operator on the reducer's string type.
*
* @subsection redstring_monoid_identity Identity
*
* The identity value of a string reducer is the empty string, which is the
* value of the expression
* `std::basic_string<Char, Traits, Alloc>([allocator])`.
*
* @section redstring_operations Operations
*
* In the operation descriptions below, the type name `String` refers to the
* reducer's string type, `std::basic_string<Char, Traits, Alloc>`.
*
* @subsection redstring_constructors Constructors
*
* Any argument list which is valid for a `std::basic_string` constructor is
* valid for a string reducer constructor. The usual move-in constructor is
* also provided:
*
* reducer(move_in(String& variable))
*
* @subsection redstring_get_set Set and Get
*
* r.set_value(const String& value)
* const String& = r.get_value() const
* r.move_in(String& variable)
* r.move_out(String& variable)
*
* @subsection redstring_initial Initial Values
*
* A string reducer with no constructor arguments, or with only an allocator
* argument, will initially contain the identity value, an empty string.
*
* @subsection redstring_view_ops View Operations
*
* *r += a
* r->append(a)
* r->append(a, b)
* r->push_back(a)
*
* These operations on string reducer views are the same as the corresponding
* operations on strings.
*
* @section redstring_performance Performance Considerations
*
* String reducers work by creating a string for each view, collecting those
* strings in a list, and then concatenating them into a single result string
* at the end of the computation. This last step takes place in serial code,
* and necessarily takes time proportional to the length of the result string.
* Thus, a parallel string reducer cannot actually speed up the time spent
* directly creating the string. This trivial example would probably be slower
* (because of reducer overhead) than the corresponding serial code:
*
* vector<string> a;
* reducer<op_string> r;
* cilk_for (int i = 0; i != a.length(); ++i) {
* *r += a[i];
* }
* string result;
* r.move_out(result);
*
* What a string reducer _can_ do is to allow the _remainder_ of the
* computation to be done in parallel, without having to worry about managing
* the string computation.
*
* The strings for new views are created (by the view identity constructor)
* using the same allocator as the string that was created when the reducer
* was constructed. Note that this allocator is determined when the reducer is
* constructed. The following two examples may have very different behavior:
*
* string<Char, Traits, Allocator> a_string;
*
* reducer< op_string<Char, Traits, Allocator> reducer1(move_in(a_string));
* ... parallel computation ...
* reducer1.move_out(a_string);
*
* reducer< op_string<Char, Traits, Allocator> reducer2;
* reducer2.move_in(a_string);
* ... parallel computation ...
* reducer2.move_out(a_string);
*
* * `reducer1` will be constructed with the same allocator as `a_string`,
* because the string was specified in the constructor. The `move_in`
* and `move_out` can therefore be done with a `swap` in constant time.
* * `reducer2` will be constructed with a _default_ allocator of type
* `Allocator`, which may not be the same as the allocator of `a_string`.
* Therefore, the `move_in` and `move_out` may have to be done with a copy
* in _O(N)_ time.
*
* (All instances of an allocator type with no internal state (like
* `std::allocator`) are "the same". You only need to worry about the "same
* allocator" issue when you create string reducers with custom allocator
* types.)
*
* @section redstring_types Type and Operator Requirements
*
* `std::basic_string<Char, Traits, Alloc>` must be a valid type.
*/
namespace cilk {
/** @ingroup ReducersString */
//@{
/** The string append reducer view class.
*
* This is the view class for reducers created with
* `cilk::reducer< cilk::op_basic_string<Char, Traits, Allocator> >`. It holds
* the accumulator variable for the reduction, and allows only append
* operations to be performed on it.
*
* @note The reducer "dereference" operation (`reducer::operator *()`)
* yields a reference to the view. Thus, for example, the view class's
* `append` operation would be used in an expression like
* `r->append(a)`, where `r` is a string append reducer variable.
*
* @tparam Char The string element type (not the string type).
* @tparam Traits The character traits type.
* @tparam Alloc The string allocator type.
*
* @see ReducersString
* @see op_basic_string
*/
template<typename Char, typename Traits, typename Alloc>
class op_basic_string_view
{
typedef std::basic_string<Char, Traits, Alloc> string_type;
typedef std::list<string_type> list_type;
typedef typename string_type::size_type size_type;
// The view's value is represented by a list of strings and a single
// string. The value is the concatenation of the strings in the list with
// the single string at the end. All string operations apply to the single
// string; reduce operations cause lists of partial strings from multiple
// strands to be combined.
//
mutable string_type m_string;
mutable list_type m_list;
// Before returning the value of the reducer, concatenate all the strings
// in the list with the single string.
//
void flatten() const
{
if (m_list.empty()) return;
typename list_type::iterator i;
size_type len = m_string.size();
for (i = m_list.begin(); i != m_list.end(); ++i)
len += i->size();
string_type result(get_allocator());
result.reserve(len);
for (i = m_list.begin(); i != m_list.end(); ++i)
result += *i;
m_list.clear();
result += m_string;
result.swap(m_string);
}
public:
/** @name Monoid support.
*/
//@{
/// Required by @ref monoid_with_view
typedef string_type value_type;
/// Required by @ref op_string
Alloc get_allocator() const
{
return m_string.get_allocator();
}
/** Reduces the views of two strands.
*
* This function is invoked by the @ref op_basic_string monoid to combine
* the views of two strands when the right strand merges with the left
* one. It appends the value contained in the right-strand view to the
* value contained in the left-strand view, and leaves the value in the
* right-strand view undefined.
*
* @param right A pointer to the right-strand view. (`this` points to
* the left-strand view.)
*
* @note Used only by the @ref op_basic_string monoid to implement the
* monoid reduce operation.
*/
void reduce(op_basic_string_view* right)
{
if (!right->m_string.empty() || !right->m_list.empty()) {
// (list, string) + (right_list, right_string) =>
// (list + {string} + right_list, right_string)
if (!m_string.empty()) {
// simulate m_list.push_back(std::move(m_string))
m_list.push_back(string_type(get_allocator()));
m_list.back().swap(m_string);
}
m_list.splice(m_list.end(), right->m_list);
m_string.swap(right->m_string);
}
}
//@}
/** @name Passes constructor arguments to the string constructor.
*/
//@{
op_basic_string_view() : m_string() {}
template <typename T1>
op_basic_string_view(const T1& x1) : m_string(x1) {}
template <typename T1, typename T2>
op_basic_string_view(const T1& x1, const T2& x2) : m_string(x1, x2) {}
template <typename T1, typename T2, typename T3>
op_basic_string_view(const T1& x1, const T2& x2, const T3& x3) : m_string(x1, x2, x3) {}
template <typename T1, typename T2, typename T3, typename T4>
op_basic_string_view(const T1& x1, const T2& x2, const T3& x3, const T4& x4) :
m_string(x1, x2, x3, x4) {}
//@}
/** Move-in constructor.
*/
explicit op_basic_string_view(move_in_wrapper<value_type> w)
: m_string(w.value().get_allocator())
{
m_string.swap(w.value());
}
/** @name @ref reducer support.
*/
//@{
void view_move_in(string_type& s)
{
m_list.clear();
if (m_string.get_allocator() == s.get_allocator())
// Equal allocators. Do a (fast) swap.
m_string.swap(s);
else
// Unequal allocators. Do a (slow) copy.
m_string = s;
s.clear();
}
void view_move_out(string_type& s)
{
flatten();
if (m_string.get_allocator() == s.get_allocator())
// Equal allocators. Do a (fast) swap.
m_string.swap(s);
else
// Unequal allocators. Do a (slow) copy.
s = m_string;
m_string.clear();
}
void view_set_value(const string_type& s)
{ m_list.clear(); m_string = s; }
string_type const& view_get_value() const
{ flatten(); return m_string; }
typedef string_type const& return_type_for_get_value;
string_type & view_get_reference()
{ flatten(); return m_string; }
string_type const& view_get_reference() const
{ flatten(); return m_string; }
//@}
/** @name View modifier operations.
*
* @details These simply wrap the corresponding operations on the underlying string.
*/
//@{
template <typename T>
op_basic_string_view& operator +=(const T& x)
{ m_string += x; return *this; }
template <typename T1>
op_basic_string_view& append(const T1& x1)
{ m_string.append(x1); return *this; }
template <typename T1, typename T2>
op_basic_string_view& append(const T1& x1, const T2& x2)
{ m_string.append(x1, x2); return *this; }
template <typename T1, typename T2, typename T3>
op_basic_string_view& append(const T1& x1, const T2& x2, const T3& x3)
{ m_string.append(x1, x2, x3); return *this; }
void push_back(const Char x) { m_string.push_back(x); }
//@}
};
/** String append monoid class. Instantiate the cilk::reducer template class
* with an op_basic_string monoid to create a string append reducer class. For
* example, to concatenate a collection of standard strings:
*
* cilk::reducer< cilk::op_basic_string<char> > r;
*
* @tparam Char The string element type (not the string type).
* @tparam Traits The character traits type.
* @tparam Alloc The string allocator type.
* @tparam Align If `false` (the default), reducers instantiated on this
* monoid will be naturally aligned (the Intel Cilk Plus library 1.0
* behavior). If `true`, reducers instantiated on this monoid
* will be cache-aligned for binary compatibility with
* reducers in Intel Cilk Plus library version 0.9.
*
* @see ReducersString
* @see op_basic_string_view
* @see reducer_basic_string
* @see op_string
* @see op_wstring
*/
template<typename Char,
typename Traits = std::char_traits<Char>,
typename Alloc = std::allocator<Char>,
bool Align = false>
class op_basic_string :
public monoid_with_view< op_basic_string_view<Char, Traits, Alloc>, Align >
{
typedef monoid_with_view< op_basic_string_view<Char, Traits, Alloc>, Align >
base;
typedef provisional_guard<typename base::view_type> view_guard;
Alloc m_allocator;
public:
/** View type of the monoid.
*/
typedef typename base::view_type view_type;
/** Constructor.
*
* There is no default constructor for string monoids, because the
* allocator must always be specified.
*
* @param allocator The list allocator to be used when
* identity-constructing new views.
*/
op_basic_string(const Alloc& allocator = Alloc()) : m_allocator(allocator)
{}
/** Creates an identity view.
*
* String view identity constructors take the string allocator as an
* argument.
*
* @param v The address of the uninitialized memory in which the view
* will be constructed.
*/
void identity(view_type *v) const
{ ::new((void*) v) view_type(m_allocator); }
/** @name Construct functions
*
* A string append reduction monoid must have a copy of the allocator of
* the leftmost view's string, so that it can use it in the `identity`
* operation. This, in turn, requires that string reduction monoids have a
* specialized `construct()` function.
*
* All string reducer monoid `construct()` functions first construct the
* leftmost view, using the arguments that were passed in from the reducer
* constructor. They then call the view's `get_allocator()` function to
* get the string allocator from the string in the leftmost view, and pass
* that to the monoid constructor.
*/
//@{
static void construct(op_basic_string* monoid, view_type* view)
{
view_guard vg( new((void*) view) view_type() );
vg.confirm_if(
new((void*) monoid) op_basic_string(view->get_allocator()) );
}
template <typename T1>
static void construct(op_basic_string* monoid, view_type* view,
const T1& x1)
{
view_guard vg( new((void*) view) view_type(x1) );
vg.confirm_if(
new((void*) monoid) op_basic_string(view->get_allocator()) );
}
template <typename T1, typename T2>
static void construct(op_basic_string* monoid, view_type* view,
const T1& x1, const T2& x2)
{
view_guard vg( new((void*) view) view_type(x1, x2) );
vg.confirm_if(
new((void*) monoid) op_basic_string(view->get_allocator()) );
}
template <typename T1, typename T2, typename T3>
static void construct(op_basic_string* monoid, view_type* view,
const T1& x1, const T2& x2, const T3& x3)
{
view_guard vg( new((void*) view) view_type(x1, x2, x3) );
vg.confirm_if(
new((void*) monoid) op_basic_string(view->get_allocator()) );
}
template <typename T1, typename T2, typename T3, typename T4>
static void construct(op_basic_string* monoid, view_type* view,
const T1& x1, const T2& x2, const T3& x3,
const T4& x4)
{
view_guard vg( new((void*) view) view_type(x1, x2, x3, x4) );
vg.confirm_if(
new((void*) monoid) op_basic_string(view->get_allocator()) );
}
//@}
};
/** Convenience typedef for 8-bit strings
*/
typedef op_basic_string<char> op_string;
/** Convenience typedef for 16-bit strings
*/
typedef op_basic_string<wchar_t> op_wstring;
/** Deprecated string append reducer class.
*
* reducer_basic_string is the same as @ref reducer<@ref op_basic_string>,
* except that reducer_basic_string is a proxy for the contained view, so that
* accumulator variable update operations can be applied directly to the
* reducer. For example, a value is appended to a `reducer<%op_basic_string>`
* with `r->push_back(a)`, but a value can be appended to a `%reducer_opand`
* with `r.push_back(a)`.
*
* @deprecated Users are strongly encouraged to use `reducer<monoid>`
* reducers rather than the old wrappers like reducer_basic_string.
* The `reducer<monoid>` reducers show the reducer/monoid/view
* architecture more clearly, are more consistent in their
* implementation, and present a simpler model for new
* user-implemented reducers.
*
* @note Implicit conversions are provided between `%reducer_basic_string`
* and `reducer<%op_basic_string>`. This allows incremental code
* conversion: old code that used `%reducer_basic_string` can pass a
* `%reducer_basic_string` to a converted function that now expects a
* pointer or reference to a `reducer<%op_basic_string>`, and vice
* versa.
*
* @tparam Char The string element type (not the string type).
* @tparam Traits The character traits type.
* @tparam Alloc The string allocator type.
*
* @see op_basic_string
* @see reducer
* @see ReducersString
*/
template<typename Char,
typename Traits = std::char_traits<Char>,
typename Alloc = std::allocator<Char> >
class reducer_basic_string :
public reducer< op_basic_string<Char, Traits, Alloc, true> >
{
typedef reducer< op_basic_string<Char, Traits, Alloc, true> > base;
using base::view;
public:
/// The reducer's string type.
typedef typename base::value_type string_type;
/// The reducer's primitive component type.
typedef Char basic_value_type;
/// The string size type.
typedef typename string_type::size_type size_type;
/// The view type for the reducer.
typedef typename base::view_type View;
/// The monoid type for the reducer.
typedef typename base::monoid_type Monoid;
/** @name Constructors
*/
//@{
/** @name Forward constructor calls to the base class.
*
* All basic_string constructor forms are supported.
*/
//@{
reducer_basic_string() {}
template <typename T1>
reducer_basic_string(const T1& x1) :
base(x1) {}
template <typename T1, typename T2>
reducer_basic_string(const T1& x1, const T2& x2) :
base(x1, x2) {}
template <typename T1, typename T2, typename T3>
reducer_basic_string(const T1& x1, const T2& x2, const T3& x3) :
base(x1, x2, x3) {}
template <typename T1, typename T2, typename T3, typename T4>
reducer_basic_string(const T1& x1, const T2& x2, const T3& x3, const T4& x4) :
base(x1, x2, x3, x4) {}
//@}
/** Allows mutable access to the string within the current view.
*
* @warning If this method is called before the parallel calculation is
* complete, the string returned by this method will be a
* partial result.
*
* @returns A mutable reference to the string within the current view.
*/
string_type &get_reference()
{ return view().view_get_reference(); }
/** Allows read-only access to the string within the current view.
*
* @warning If this method is called before the parallel calculation is
* complete, the string returned by this method will be a
* partial result.
*
* @returns A const reference to the string within the current view.
*/
string_type const &get_reference() const
{ return view().view_get_reference(); }
/** @name Appends to the string.
*
* These operations are simply forwarded to the view.
*/
//@{
void append(const Char *ptr)
{ view().append(ptr); }
void append(const Char *ptr, size_type count)
{ view().append(ptr, count); }
void append(const string_type &str, size_type offset, size_type count)
{ view().append(str, offset, count); }
void append(const string_type &str)
{ view().append(str); }
void append(size_type count, Char ch)
{ view().append(count, ch); }
// Appends to the string
reducer_basic_string<Char, Traits, Alloc> &operator+=(Char ch)
{ view() += ch; return *this; }
reducer_basic_string<Char, Traits, Alloc> &operator+=(const Char *ptr)
{ view() += ptr; return *this; }
reducer_basic_string<Char, Traits, Alloc> &operator+=(const string_type &right)
{ view() += right; return *this; }
//@}
/** @name Dereference
* @details Dereferencing a wrapper is a no-op. It simply returns the
* wrapper. Combined with the rule that the wrapper forwards view
* operations to its contained view, this means that view operations can
* be written the same way on reducers and wrappers, which is convenient
* for incrementally converting old code using wrappers to use reducers
* instead. That is:
*
* reducer<op_string> r;
* r->push_back(a); // r-> returns the view
* // push_back() is a view member function
*
* reducer_string w;
* w->push_back(a); // *w returns the wrapper
* // push_back() is a wrapper member function
* // that calls the corresponding view function
*/
//@{
reducer_basic_string& operator*() { return *this; }
reducer_basic_string const& operator*() const { return *this; }
reducer_basic_string* operator->() { return this; }
reducer_basic_string const* operator->() const { return this; }
//@}
/** @name Upcast
* @details In Intel Cilk Plus library 0.9, reducers were always cache-aligned.
* In library 1.0, reducer cache alignment is optional. By default,
* reducers are unaligned (i.e., just naturally aligned), but legacy
* wrappers inherit from cache-aligned reducers for binary compatibility.
*
* This means that a wrapper will automatically be upcast to its aligned
* reducer base class. The following conversion operators provide
* pseudo-upcasts to the corresponding unaligned reducer class.
*/
//@{
operator reducer< op_basic_string<Char, Traits, Alloc, false> >& ()
{
return *reinterpret_cast< reducer<
op_basic_string<Char, Traits, Alloc, false> >*
>(this);
}
operator const reducer< op_basic_string<Char, Traits, Alloc, false> >& () const
{
return *reinterpret_cast< const reducer<
op_basic_string<Char, Traits, Alloc, false> >*
>(this);
}
//@}
};
/** Convenience typedef for 8-bit strings
*/
typedef reducer_basic_string<char> reducer_string;
/** Convenience typedef for 16-bit strings
*/
typedef reducer_basic_string<wchar_t> reducer_wstring;
/// @cond internal
/// @cond internal
/** Metafunction specialization for reducer conversion.
*
* This specialization of the @ref legacy_reducer_downcast template class
* defined in reducer.h causes the `reducer< op_basic_string<Char> >` class to
* have an `operator reducer_basic_string<Char>& ()` conversion operator that
* statically downcasts the `reducer<op_basic_string>` to the corresponding
* `reducer_basic_string` type. (The reverse conversion, from
* `reducer_basic_string` to `reducer<op_basic_string>`, is just an upcast,
* which is provided for free by the language.)
*
* @ingroup ReducersString
*/
template<typename Char, typename Traits, typename Alloc, bool Align>
struct legacy_reducer_downcast<
reducer<op_basic_string<Char, Traits, Alloc, Align> > >
{
typedef reducer_basic_string<Char, Traits, Alloc> type;
};
/// @endcond
//@}
} // namespace cilk
#endif // REDUCER_STRING_H_INCLUDED